1. Field of the Invention
This invention relates to a thin film magnetic head, particularly to a magnetoresistive effective type thin film magnetic head and a method for fabricating the same.
2. Related Art Statement
As a magnetic conversion device employed in a hard disk driving device, a combination type thin film magnetic head, where an inductive type thin film magnetic head element for writing and a magnetoresistive effective type thin film magnetic head element are stacked on a given substrate in turn, is widely available. With the development of the surface recording density of such a hard disk driving device, the performance of such a combination type thin film magnetic head is required to be developed. As a magnetoresistive effective type thin film magnetic head element, an AMR element utilizing normal anisotropic magnetoresistive effect is usually employed, but recently, a GMR element utilizing giant magnetoresistive effect several times as large as the normal anisotropic magnetoresistive effect is developed and widely available.
In the AMR element, surface recording density of several giga bits/inch2 can be realized, and in the GMR element, the surface recording density can be more enhanced. As a result, a large capacity hard disk driving device having a capacity of several ten giga bits or over can be realized.
As of now, various types of GMR element are proposed, but particularly attention is paid to a spin-valve GMR element. In the spin-valve GMR element, longitudinal bias-applying films are formed in both sides of a magnetoresistive effective film (MR film). In some cases, both edges of the MR film are covered with electrode films. In this case, the distance between the electrode films is set smaller than the distance between the longitudinal bias-applying films. Such an element structure is usually called as a xe2x80x9clead overlay structurexe2x80x9d, and is disclosed in Japanese Patent Applications Laid-open Hei 8-45037 (JP A 8-45037) and Hei 9-282618 (JP A 9-282618). Such a lead overlay structure is employed in an AMR element as well as the spin-valve GMR element. In a magnetoresistive effective type thin film magnetic head having such a lead overlay structure, Barkhausen noise can be repressed effectively and fluctuation in output power can be reduced. Therefore, the sensitivity of the thin film magnetic head can be enhanced.
In fabricating the magnetoresistive effective type thin film magnetic head having the lead overlay structure, two uniform films are formed and patterned to form the longitudinal bias-applying films and the electrode films, respectively. In this case, that is, two photolithography steps are required. Normally, the longitudinal bias-applying films are formed and thereafter, the electrode films are formed. As mentioned above, since the distance between the electrode films is set smaller than the distance between the longitudinal bias-applying films, the above photolithography steps are difficult and thus, the longitudinal bias-applying films and the electrode films can not be patterned precisely.
Particularly, in forming the electrode films, the surface level of the MR film is different from the surface level of the longitudinal bias-applying films. Therefore, it is more difficult to form the electrode films precisely due to the steps created between the MR film and the longitudinal bias-applying films, so that the magnetoresistive effective type thin film magnetic head can not be fabricated stably on a wafer as a substrate.
It is an object of the present invention to mitigate the defect in the above conventional fabricating method and thus, to provide a thin film magnetic head including a magnetoresistive effective type thin film magnetic head element of stable output power level.
It is another object of the present invention to provide a method for fabricating stably a thin film magnetic head including a magnetoresistive effective type thin film magnetic head element of a desired output power level.
For achieving the above objects, this invention relates to a thin film magnetic head including a magnetoresistive effective type thin film magnetic head element comprising:
a first and a second magnetic shielding films which are made of magnetic material,
a first and a second shielding gap films which are made of non-magnetic insulating material and located between the first and the second magnetic shielding films,
a magnetoresistive effective element film which is located between the first and the second shielding gap films,
a first and a second longitudinal bias-applying films which are located in both sides of the magnetoresistive effective element film, and
a first and a second electrode films which are located so as to cover edge portions of the magnetoresistive effective element film beyond the first and the second longitudinal bias-applying films, wherein
the difference in surface level between the magnetoresistive effective element film and the first and second longitudinal bias-applying films is set within xc2x120 nm.
Also, this invention relates to a method for fabricating a thin film magnetic head including a magnetoresistive effective type thin film magnetic head element comprising a first and a second magnetic shielding films which are made of magnetic material, a first and a second shielding gap films which are made of non-magnetic insulating material and located between the first and the second magnetic shielding films, a magnetoresistive effective element film which is located between the first and the second shielding gap films, a first and a second longitudinal bias-applying films which are located in both sides of the magnetoresistive effective element film, and a first and a second electrode films which are located so as to cover edge portions of the magnetoresistive effective element film beyond the first and the second longitudinal bias-applying films, comprising the steps of:
forming the first shielding film on a given substrate,
forming the first shielding gap film on the first shielding film,
forming a magnetoresistive effective film on the first shielding gap film,
partially etching and removing the magnetoresistive effective film via a first mask fabricated thereon to pattern and form the magnetoresistive effective element film,
forming the first and the second longitudinal bias-applying films via the first mask at both sides of the magnetoresistive effective element film so that the difference in surface level between the magnetoresistive effective element film and the first and the second longitudinal bias-applying films is set within xc2x120 nm,
forming the first and the second electrode films so as to cover edge portions of the magnetoresistive effective element film and the first and the second longitudinal bias-applying films,
forming the second shielding gas film so as to cover the magnetoresistive effective element film, the first and the second electrode films, and
forming the second shielding film on the second shielding gap film.
The inventors confirmed on many researches that if the difference in surface level between the MR film and the first and second longitudinal bias-applying films is set within xc2x120 nm, the first and second electrode films can be patterned and formed on a wafer as a substrate as designed. Therefore, many thin film magnetic heads can be fabricated on the same wafer as designed in dimension. As a result, since the distance between the first and the second electrode films can be defined precisely in each thin film magnetic head, the track width can be formed minutely and precisely as designed because it is defined by the distance between the first and the second electrode films.
The first and the second longitudinal bias-applying films are composed of hard magnetic films, underfilms for controlling the orientations of the hard magnetic films and protective films to protect the hard magnetic films, respectively. The thickness of the hard magnetic film is determined on the design specification of the thin film magnetic head, so can not be changed. For setting within xc2x120 nm the difference in surface level between the MR film and the first and second longitudinal bias-applying films, therefore, the thickness of the underfilm and/or the protective film may be controlled. Moreover, in the etching step for forming the MR film, the etching depth of the first shielding gap film which is located under the MR film may be controlled. These controlling means may be combined appropriately.
In the thin film magnetic head of the present invention, since the first and the second electrode films can be patterned and formed precisely, the track width defined by the distance between the first and the second electrode films can be narrowed. In a preferred embodiment of the present invention, the track width can be reduced up to 0.2 xcexcm or below.
The thin film magnetic head may be preferably fabricated as a combination type thin film magnetic head where on a given substrate, are stacked a magnetoresistive effective type thin film magnetic head element for reading according to the present invention and an inductive type thin film magnetic head element for writing. The stacking order is not restricted. Normally, the inductive type thin film magnetic head element may be stacked on the magnetoresistive effective type thin film magnetic head element fabricated on the substrate (normal type). Reversely, the magnetoresistive effective type thin film magnetic head element may be stacked on the inductive type thin film magnetic head fabricated on the substrate (reversed type).